1. Technical Field
The present invention relates to a transfer device for transferring liquid developer image transferred on an image carrier belt onto a transfer material such as paper, and to an image forming apparatus including the transfer device.
2. Related Art
Currently, such a type of liquid developer image forming apparatus has been proposed which includes a transfer unit for transferring a liquid developer image transferred on an image carrier belt onto a transfer material such as paper (for example, see JP-A-2001-166611). According to the transfer device included in the image forming apparatus disclosed in JP-A-2001-166611, a transfer roller is pressed against the image carrier belt such that the image carrier belt can be wound around the transfer roller. As a result, a circular arc transfer nip having a nip shape and a predetermined width in the shift direction of the transfer material is produced to provide preferable transfer characteristics.
According to the transfer device included in the image forming apparatus shown in JP-A-2001-166611, the transfer nip having a certain width is obtained in the shift direction of the transfer material. However, the possible width of the transfer nip to be produced is limited due to the structure which winds the image carrier belt around the transfer roller. Thus, improvement over the transfer efficiency is limited and difficult to be further raised.
Additionally, since the nip shape of the transfer nip is a circular arc having the same radius of curvature as that of the transfer roller and the predetermined width, the transfer material reaching the transfer nip is forcefully curved into a circular arc having the same shape. Thus, passing smoothness and separability of the transfer material at the transfer nip are not preferable. Moreover, a part of liquid developer on the image carrier belt reaches the end of the transfer roller at the time of transfer, thereby causing deterioration of the image.